[QUANTITY]Re: Quantity.owl

[Brian Thomas]

> > >
> > > is this the simple quantity class/concept that Ray want to subclass?
> > > I must admit I am afraid, and for me it seems more related to
> > > the analysis of a global structure concerning the more general
> > > concept of VOData, related to [OBSERVATIONS] theme.
> >
> > 	Yes, this is directly related to Ray's quantity DM proposal.
>
> Does Ray contribute to this proposition?

	I have talked with Ray on occaison, but no, he is not formally part
	of the proposition. Im not sure why that matters however..

>
> >	The quantity
> > 	we propose is a very reusable class that may be mapped into tables,
> > 	spectra, images, parameters, etc. Even algorithmic representation is
> > 	possible with this model.
>
> It seems very complex and quite diff. from a basic DM stone
> as previously forseen for quantity, it implicitly implies a lot of
> design decission without any consensus.

	Its not complex. It just means that you have a few objects that may
	serve as powerful building blocks. I find having many special purpose
	classes to be the complex solution. In that case, you get an explosion
	of sub-classes. The fewer base classes the better.

>
> > 	Why afraid? These things have to tie together at some point. Our
> > 	view is that the UCD are concepts that will inherit (as a class)
> >	from the quantities
>
> Will VO specialists and CDS agree on that?
	
	I hope so. Why wouldnt they? 
>
> > 	in the DM. This allows people in the VO to describe ALL of thier
> > holdings in terms of UCDs (not just the columns on their tables).
> > Interface documents, in XML, based in the quantity DM, can be used for
> > searching data repositories.
>
> Is this really the original purpose of quantity?

	Im sorry, if this isnt, what is the original purpose? I think the point
	is to develop a data model that may serve to transport information
	across the internet AND to serve as a basis for search of data repositories.
	Having the UCD's inherit from a 'quantity' seems to match well with these
	fundemental requirements. I think focusing on replication of data formats
	is a red herriing.  The community should be looking at passing around fundemental
	atoms of information (e.g. the quantity). Take for example a search for 
	bright galaxies in a sky region. IF you focus on looking for "images" you will
	be missing out on sky photometry that can be peiced together to look like
	an image. Its information about flux that  is related to some sky position that you are
	really after, not 'images'.

	What did you think the original purpose of quantity was?

>
> > 	I have a draft of our position paper that I hope to release publically
> > soon. I will have a poster on this work at the ADASS. Please come by :)
>
> I will not attend ADASS.
> PD

					-b.t.

-- 

  * Dr. Brian Thomas 

  * Code 630.1 
  * Goddard Space Flight Center NASA

  *   fax: (301) 286-1775
  * phone: (301) 286-6128